Method of and apparatus for manufacturing polarization plate

ABSTRACT

When a polarization plate is manufactured by laminating and laminating at least two types of retarder onto a polarizer by a laminating apparatus, the two films of at least the two types of the retarder including at least the polarizer are laminated such that the difference of the angle between the drawing directions of the two films is within the range of 40° to 80°. With this arrangement, a good handling property can be obtained, improvement of a yield ratio can be expected, the installation area of the laminating apparatus can be reduced due to reduction in size of the laminating apparatus.

TECHNICAL FIELD

The present invention relates to a method of and an apparatus formanufacturing a polarization plate composed of a polarizer onto which atleast two retarder having a different drawing direction are laminated.

BACKGROUND ART

A polarization plate composed of a polarizer onto which a retarder islaminated and laminated is used as an optical component constituting,for example, a liquid crystal display device (refer to, for example,Patent Document 1). The polarization plate, which is used in a TN(twisted nematic) type liquid crystal display device, a semi-transparentreflection type display device, and the like, is often composed of apolarization plate onto which a retarder is laminated. In thepolarization plate, it is known that the angle of a drawing direction ofthe retarder to the polarizer is 15°±10°, 75°±10°.

Patent Document 1: Japanese Patent Application Laid-Open No. 11-231129(pages 2 to 3)

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

Incidentally, since a retarder, which is cut off for laminating, may beformed in a very slender parallelogram shape depending on the angle ofthe retarder to be laminated a polarizer, there is a high possibilitythat a handling property is deteriorated before the retarder islaminated, that is, a yield is lowered.

Since the cut-out retarder is formed in a very slender parallelogramshape likewise, a problem arises in that the size of an apparatus formanufacturing it is increased, that is, the cost of the apparatus isincreased, and the like.

Accordingly, an object of the present invention, which was made in viewof the above circumstances, is to provide such a method of and anapparatus for manufacturing a polarization plate that a good handlingproperty can be obtained, improvement of a yield ratio can be expected,and the size and the installation area of the apparatus can be reduced.

Means for Solving the Problems

To overcome the problems, the present invention is arranged as describedbelow.

An invention according to claim 1 is characterized by a method ofmanufacturing a polarization plate by laminating and laminating at leasttwo types of retarder onto a polarizer, wherein the two films of atleast the two types of the retarder including at least the polarizer arelaminated such that the difference of the angle between the drawingdirections of the two films is within the range of 40° to 80°.

An invention according to claim 2 is characterized in a method ofmanufacturing a polarization plate according to claim 1, wherein theangle of at least one of the retarder in the drawing direction thereofto the polarizer is 15°±10° or 75°±10°.

An invention according to claim 3 is characterized in an apparatus formanufacturing a polarization plate by laminating and laminating at leasttwo types of retarder onto a polarizer, wherein the apparatus iscomposed of a polarizer transport means for transporting the polarizer,a retarder transport means for transporting at least the two retarder,and a laminate/punch means for laminating and punching the two films ofat least the two types of the retarder including at least the polarizersuch that the difference of the angle between the drawing directions ofthe two films is within the range of 40° to 80°.

An invention according to claim 4 is characterized in an apparatus formanufacturing a polarization plate according to claim 3, wherein theangle of at least one of the retarder in the drawing direction thereofto the polarizer is 15°±10° or 75°±10°.

Effect of the Invention

With the above arrangements, the present invention has the followingeffects.

According to the inventions of claims 1 and 3, since the two films of atleast the two types of the retarder including at least the polarizer arelaminated such that the difference of the angle between the drawingdirections of the two films is within the range of 40° to 80°, thelaminated films are not made to, for example, an extremely slenderparallelogram shape. Accordingly, a good handling property can beobtained and improvement of a yield ratio can be expected as well sincethe size of the apparatus can be reduced, an increase in length of theapparatus can be prevented by reducing the installation area thereof.

According to the inventions of claims 2 and 4, the polarization platecan be obtained using at least the two types of the retarder having adifferent drawing direction in which the angle of at least one of theretarder in the drawing direction thereof to the polarizer is 15°±10° or75°±10°.

Best Mode for Carrying Out the Invention

An embodiment of a method of and an apparatus for manufacturing apolarization plate of the present invention will be explained below indetail based on drawings. Although the embodiment of the presentinvention shows a most preferable mode of the invention, the inventionis not limited thereto.

FIG. 1 is a side elevational view of the polarization platemanufacturing apparatus when a polarizer and at least two types ofretarder in the embodiment are supplied in a roll state and used,respectively and a laminated product is obtained in the roll state. FIG.2 is a top view of the polarization plate manufacturing apparatus.

A strip-shaped film 12 composed of a polarizer 12 b and a release film12 a having a sticky agent applied thereto and laminated the polarizer12 b is unwound from an unwinder 10 through nip rolls 14. The releasefilm 12 a is removed from the film 12 by a rewinding roll 16 along thenip rolls 14, and the polarizer 12 b to which the sticky agent isapplied is supplied to a laminate/punch device 24 constituting alaminate/punch means through free rolls 20 and 22, thereby a polarizertransport means for transporting the polarizer 12 b is arranged.

A light source 26 composed of an incandescent lamp, a polarizationdevice 28, and a photodetector 30 composed of a photodiode are disposedbetween the free rolls 20 and 22 to detect and control the angle of thepolarizer 12 b. More specifically, the absorption axis of thepolarization device 28 is disposed in parallel with the roll axes of theunwinder 10, the nip rolls 14, and the free rolls 20 and 22, the angleof the polarizer 12 b is controlled by an axially-movable rubber griproll 32 so that the intensity of light detected by the photodetector 30is minimized, and then the polarizer 12 b is wound by a rewinder 34.These rolls and devices are mounted on and supported by a frame 36.

In contrast, two types of strip-shaped retarder 42 a, 42 b are rewoundfrom an unwinder 40 through nip rolls 44. The retarder 42 a, 42 b aresupplied to a position on the polarizer 12 b, to which the sticky agentis applied, above the laminate-punch unit 24 at a predetermined gapthrough free rolls 46 and 48, thereby a retarder transport means fortransporting the retarder 42 a, 42 b is arranged.

A light source 50 composed of an incandescent lamp, a polarizationdevice 52, a polarizer 54 disposed such that the absorption axis thereofis orthogonal to the polarization device 52, and a photodetector 56composed of a photodiode are disposed between the free rolls 46 and 48so that the angle of a retarder 42 is detected and controlled. Morespecifically, the absorption axis of the polarization device 52 isdisposed in parallel with the roll axes of the unwinder 40, the niprolls 44, and the free rolls 46 and 48, the angles of the retarder 42 a,42 b are controlled by a pair of axially-movable nip rolls 58 so thatthe intensity of light detected by the photodetector 56 is minimized,and the retarder 42 is wound by a rewinder 60. These rolls and thedevices are mounted on and supported by a frame 62.

The direction in which the retarder 42 a, 42 b are transported and thedirection in which the polarizer 12 b is transported can be set to havean arbitrary angle by changing the angle between the frames 36 and 62according to an object of an optical film to be manufactured. After atarget angle is set as described above, the angle can be controlled witha high accuracy by optically detecting the actual angle between thefilms as described above and minutely adjusting it.

Both the films are laminated by the laminate/punch unit 24 and only theretarder 42 a, 42 b are cut off by being punched out.

FIG. 3 is an enlarged view of the laminate/punch unit 24 as well as asectional view observed from a direction from which the polarizer 12 bis transported. FIG. 4 is an enlarged view of the laminate/punch unit 24and as well as a sectional view observed from a direction from which theretarder 42 a, 42 b are transported likewise.

When a pressure plate 70 moves upward, the polarizer 12 b is laminatedthe retarder 42 a, 42 b by predetermined pressure. Subsequently, acutting blade 72 moves upward and cuts off only the retarder 42 a, 42 bto the width of the polarizer 12 b. Next, the cutting blade 72 movesdownward and returns to an initial position, and a cutting blade 78moves downward by the thickness of the retarder 42 a, 42 b and cuts offonly the retarder 42. At the time, the retarder 42 a, 42 b are punchedout remaining a continuous ear portion so that the angle thereof can becontrolled by the nip rolls 58. In the boding/punching operation,transportation of the polarizer 12 b and the retarder 42 a, 42 b istemporarily stopped.

A product, which is composed of the polarizer 12 b and the retarder 42a, 42 b laminated the polarizer 12 b, is rewound by the rewinder 34 inthe roll state. In contrast, the remaining ear portion from which theretarder 42 a, 24 b are cut off is rewound by the rewinder 60. Theroll-state laminated product can be obtained as described above.

FIG. 5 is a view showing an embodiment in which two types ofstrip-shaped retarder are laminated and laminated onto a strip-shapedpolarizer. In the embodiment, the retarder 42 a, 42 b are laminated thestrip-shaped polarizer 12 b such that the difference of the anglebetween drawing directions is within the range of 40° to 80°. In theembodiment, the two types of the retarder 42 a, 42 b may have the samedrawing direction or a different drawing direction, and they aretransported in a laminated state.

FIG. 6 shows a product composed of the polarizer onto which the retarderis laminated as described above, wherein a part (a) shows plan view and(b) shows a side elevational view. The punched-out retarder 42 a, 42 bare laminated the continuous polarizer 12 b.

As shown in FIGS. 5 and 6, the product composed of the polarizer ontowhich the retarder is laminated is not formed in an extremely slenderparallelogram shape A as the laminated shape of the product. Since theparallelogram shape A as the laminated shape is an approximately regularparallelogram shape, a good handling property can be obtained andimprovement of a yield ratio can be expected. Further, the size of thelaminate/punch device 24 can be reduced because the parallelogram shapeA is not made to an extremely slender shape, thereby an increase oflength of the apparatus can be prevented because the installation areaof the apparatus can be reduced.

In the embodiment, the polarization plate of the product, in which theangle of the two the retarder 42 a, 42 b in the drawing directionthereof is 75°±10° to the polarizer 12 b and the retarder 42 a, 42 b arelaminated the polarizer 12 b, can be obtained.

FIG. 7 is a view showing another embodiment of at least two types ofstrip-shaped retarder laminated and laminated onto a strip-shapedpolarizer. In the embodiment, the two types of the retarder 42 a, 42 bare laminated the strip-shaped polarizer 12 b while being individuallytransported from different directions.

In the embodiment, the two types of the retarder 42 a, 42 b in thedifferent drawing directions are laminated such that the difference ofthe angle between the drawing directions is within the range of 40° to80°. It is possible to obtain a product of a polarization plate in whichthe angle of the retarder 42 a on one hand in the drawing directionthereof to the polarizer 12 b is 15°±10°, the angle of the retarder 42 bon the other hand in the drawing direction thereof to the polarizer 12 bis 75°±10°, and the retarder 42 a, 42 b are laminated the polarizer 12b.

The fundamental structure of the polarizer used in the embodiment is asshown in FIG. 8. The strip-shaped polarizer 12 b has such a structurethat a polarizer film 12 b 1, which is, for example, a polarizationlayer and composed of PVA (polyvinyl alcohol) and the like, issandwiched between two TAC (triacetyl cellulose) films 12 b 11, 12 b 12as cellulose films. In the polarizer 12 b, a sticky layer 12 b 13 isformed on the outside surface of the TAC film 12 b 13 on one hand, therelease film 12 a is laminated the sticky layer 12 b 13. Further, aprotection film 12 c is laminated the outside surface of the TAC film 12b 12 on the other hand. Note that the polarizer film 12 b is coloredwith, for example, iodine, a dichroic dye, and the like to shut offlight other than the light vibrating in a given direction.

The fundamental structure of the strip-shaped retarder used in theembodiment is as shown in FIG. 9. The strip-shaped retarder 42 a, 42 bare retarder containing, for example, polycarbonate, polyethersulfone,and the like as a phase difference layer 42 c 1. Each of the retarder 42a, 42 b has a protection film 42 c 2 laminated an outside surfacethereof as well as a sticky layer 42 c 3 disposed on the other outsidesurface thereof so as to be laminated a liquid crystal display device,and a release film 42 c 4 is laminated the sticky layer 42 c 3.

The fundamental structure of the product of the polarization plate inwhich the retarder 42 a, 42 b are laminated the polarizer 12 b is asshown in FIG. 10. The release film 12 a is removed from the polarizer 12b, and protection films 20 b are removed from the retarder 42 a, 42 b,respectively, and the polarizer 12 b is laminated the retarder 42 athrough the sticky layer 42 c 3. Further, the retarder 42 b is laminatedthe retarder 42 a.

In the present invention, the types of the retarder to be laminate arenot limited as long as a polarization plate, in which at least two typesof retarder are laminated the polarizer 12 b, is manufactured. Further,in the structure, since the two films of at least the two types of theretarder including at least the polarizer are laminated such that thedifference of the angle between the drawing directions of the two filmsis within the range of 40° to 80°, laminating is carried out so that thedifference of the angle between the polarizer and the drawing directionof any of the retarder or the difference of the angle between thedrawing directions of the retarder is within the range of 40° to 80°.

INDUSTRIAL APPLICABILITY

In the present invention, since the two films of at least the two typesof the retarder including at least the polarizer are laminated such thatthe difference of the angle between the drawing directions of the twofilms is within the range of 40° to 80°, they are not laminated in, forexample, an extremely slender parallelogram shape. Accordingly, a goodhandling property can be obtained and improvement of a yield ratio canbe expected as well since the size of the apparatus can be reduced, anincrease in length of the apparatus can be prevented by reducing theinstallation area thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of an apparatus for manufacturing apolarization plate when a polarizer and at least two types of retarderof the present invention are supplied in a roll state and used,respectively and a laminated product is obtained in the roll state.

FIG. 2 is a top view of the polarization plate manufacturing apparatuswhen the polarizer and at least the two types of the retarder of thepresent invention are supplied in the roll state and used, respectivelyand the laminated product is obtained in the roll state.

FIG. 3 is an enlarged view of a laminate/punch unit of the apparatus formanufacturing the polarization plate of the present invention as well asa sectional view observed from a direction from which the polarizer istransported.

FIG. 4 is an enlarged view of the laminate/punch unit of the apparatusfor manufacturing the polarization plate of the present invention aswell as a sectional view observed from a direction from which theretarder are transported.

FIG. 5 is view showing an embodiment in which the two types of thestrip-shaped retarder are laminated and laminated onto the strip-shapedpolarizer.

FIG. 6 shows a product composed of the polarizer on which the retarderare laminated, wherein a part (a) is a plan view, and part (b) is a sideelevational view.

FIG. 7 is a view showing another embodiment in which at least the twotypes of the strip-shaped retarder are laminated and laminated onto thestrip-shaped polarizer.

FIG. 8 is a view showing the fundamental structure of the polarizer usedin the embodiment.

FIG. 9 is a view showing the fundamental structure of the strip-shapedretarder used in the embodiment.

FIG. 10 is a view showing the fundamental structure of the polarizationplate of the product composed of the polarizer on which the retarder arelaminated.

REFERENCE NUMERALS

-   10 unwinder-   12 film-   12 a release film-   12 b polarizer-   12 c protection film-   24 laminate/punch unit-   26 light source-   28 polarization device-   30 photodetector-   34 rewinder-   40 unwinder-   42 a, 42 b retarder-   50 light source-   52 polarization device-   54 polarizer-   56 photodetector-   60 rewinder

1. A method of manufacturing a polarization plate by laminating andlaminating at least two types of retarder onto a polarizer,characterized in that the two films of at least the two types of theretarder including at least the polarizer are laminated such that thedifference of the angle between the drawing directions of the two filmsis within the range of 40° to 80°.
 2. A method of manufacturing apolarization plate according to claim 1, characterized in that the angleof at least one of the retarder in the drawing direction thereof to thepolarizer is 15°±10° or 75°±10°.
 3. An apparatus for manufacturing apolarization plate by laminating and laminating at least two types ofretarder onto a polarizer, characterized by comprising: a polarizertransport means for transporting the polarizer; a retarder transportmeans for transporting at least the two retarder; and a laminate /punchmeans for laminating and punching the two films of at least the twotypes of the retarder including at least the polarizer such that thedifference of the angle between the drawing directions of the two filmsis within the range of 40° to 80°.
 4. An apparatus for manufacturing apolarization plate according to claim 3, characterized in that the angleof at least one of the retarder in the drawing direction thereof to thepolarizer is 15°±10° or 75°±10°.